#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>

int main() {
    using namespace std;
    auto perm_gcd = [&](string s) -> string {
        int n = s.size();
        sort(s.begin(), s.end());
        if (s[0] == s[n - 1]) { return s; }
        int g = s[n - 1] - '0', tot = 0;
        for (char c : s) {
            g = gcd(g, c - '0');
            tot = (tot + c - '0') % 9;
        }
        if (tot > 0) { return "1"; }
        if (g < 9) { return to_string(g * 9); }
        return "9";
    };

    string s;
    cin >> s;
    cout << perm_gcd(s) << endl;
}